Biological capsule reentered 7/7/69. The intent had been to fly a 6 kg male pig-tailed monkey (Macaca nemestrina) named Bonnie in Earth-orbit for 30 days. However, after only 8.8 days in orbit, the mission was terminated because of the subject's deteriorating health. High development costs were a strong incentive for maximising the scientific return from the mission. Because of this, the scientific goals had become exceedingly ambitious over time, and a great many measurements were conducted on the single research subject flown. Although the mission was highly successful from a technical standpoint, the science results were apparently compromised.

Despite the seeming failure of the mission's scientific agenda, Biosatellite III was influential in shaping the life sciences flight experiment program, pointing to the need for centralised management, realistic goals and substantial pre-flight experiment verification testing. The mission objective was to investigate the effect of space flight on brain states, behavioural performance, cardiovascular status, fluid and electrolyte balance, and metabolic state.